A study of the use of aspherics in the design of double Gauss lenses optimized at ƒ/2 with a total field of view of 42° has been performed. Several specific designs incorporating one or two aspheric surfaces at different positions in the lens are presented. The aspheric designs yield substantially increased resolution as compared with an optimized spherical system.
T. R. Sloan and R. E. Hopkins, "Design of Double Gauss Systems Using Aspherics," Appl. Opt. 6, 1911-1916 (1967)